This invention relates to valves, and in particular to valves for fluid dispensing systems.
One type of valve typically used in fluid dispensing systems, for example systems used to distribute fertilizers, pesticides, and herbicides, comprises a valve spool with a number of o-rings on it, which reciprocates in a valve housing. However, the friction caused by the rubbing of the o-rings against the valve housing not only causes wear, but also requires a relatively large force to bias the valve closed. This means that a relatively large force is required to operate the valve, which is fatiguing to the user.
It is also desirable that valves used in fluid dispensing systems be of very simple construction so that the fluids passing through the valves do not foul the valves or interfere with their operation. This is important because fluid dispensing systems are often subject to in-service abuse and may not be well maintained. For example, the system may not be properly cleaned after each use, allowing residual amounts of fluids to dry in the valve. This means that it is desirable that as few parts of the valve as possible come in contact with the fluid. Moreover, it means that the valve should be constructed so that it is relatively easy to clean, and so that it can withstand substantial back pressures that may be used to clean the valve.